A top-secret U.S. Army Special Operations unit has been running covert missions all over the world, from leading death squads to the hideout of drug baron Pablo Escobar to assassinating key al Qaeda members, including Iraqi leader Abu Musab al-Zarqawi, and, in one of their greatest missions, capturing Saddam Hussein. 'The Activity," as it became known to insiders, has achieved near-mythical status, even among the world's Special Operations elite...